The soft skin at the back of the scrotum. It is usually bald, but occasionally hairy. The olb is not to be mistaken for the gooch, as the olb is part of the scrotum, not the skin between the scrotum and rectum.

I was relaxing, gently caressing my olb, then I proceeded to shove my hand in the slut's face and forced her to savor the sour, yet all too familiar odor.